Public Utilities, Approved Additional Generating Capacity

No definition available.

Name:	so_PublicUtilitiesApprovedAdditionalGeneratingCapacity
Namespace Prefix:	so_
Data Type:	dtr-types1:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Utilities, Required Fossil-stream Generation Retirements

+ References

No definition available.

+ Details

Name:	so_PublicUtilitiesRequiredFossilStreamGenerationRetirements
Namespace Prefix:	so_
Data Type:	dtr-types1:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479960/980-360-S99-1

+ Details

Name:	us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481878/980-340-50-1

+ Details

Name:	us-gaap_NetRegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=so_MississippiPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=so_PlantWatsonUnit4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=so_PlantGreeneCountyUnits1And2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=so_AlabamaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=so_PlantDanielUnits1And2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

REGULATORY MATTERS - MPC Integrated Resource Plan (Details) $ in Millions	1 Months Ended
	Oct. 31, 2023 MW	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 MW	Dec. 31, 2020 MW
Public Utilities, General Disclosures [Line Items]
Net regulatory assets \| $		$ 6,523	$ 5,833
Mississippi Power
Public Utilities, General Disclosures [Line Items]
Required fossil-stream generation retirements (in MWs)					950
Net regulatory assets \| $		90	$ 4
Approved additional generating capacity (in MW)	750
Mississippi Power \| Plant Watson Unit 4
Public Utilities, General Disclosures [Line Items]
Required fossil-stream generation retirements (in MWs)				268
Mississippi Power \| Plant Greene County Units 1 and 2
Public Utilities, General Disclosures [Line Items]
Required fossil-stream generation retirements (in MWs)				103
Percent ownership				40.00%
Mississippi Power \| Plant Greene County Units 1 and 2 \| Alabama Power
Public Utilities, General Disclosures [Line Items]
Percent ownership				40.00%
Mississippi Power \| Plant Daniel
Public Utilities, General Disclosures [Line Items]
Required fossil-stream generation retirements (in MWs)				502
Percent ownership				50.00%
Net regulatory assets \| $		$ 489